The present invention relates generally to the field of irrigation, and more specifically to a thrust plug that performs two functions, namely (i) plugging an opening in a fluid delivery system (e.g., an open orifice of a fitting or coupling) and (ii) providing a surface against which a concrete thrust block can be cast. The thrust plug of the present invention preferably reversibly plugs the opening in the fluid delivery system.
Thrust blocking is well known in the art of gasketed o-ring connection irrigation systems, e.g., municipal water systems and golf course irrigation systems. It is well known that water under pressure can exert thrust forces in piping systems, especially as the system is activated and pressurized. In a typical four-inch PVC 150 p.s.i. system, peak pressures of about 200 p.s.i. are not uncommon, which can generate thrust forces of about 13,000 pounds. To counteract these thrust forces, concrete thrust blocks are typically cast in place at each change in direction or increase in pressure of a pipe line, including but not limited to at all reducers, tees, crosses, plugs, end caps, elbows (of various degrees), tees used as elbows, crosses used as elbows, Y-connections, valve anchors, etc. These concrete thrust blocks are typically cast between undisturbed earth and one of the fittings listed above.
Thrust blocking is especially important for gasket and o-ring systems in which the only restraining forces which are available to counteract thrust forces are forces provided by friction and burial. Neither of these forces is capable of counter balancing the force created by the internal hydraulic pressure of the system. Paragraph 6.1 of ANSI/ASTM F690, xe2x80x9cPractice for Underground Installation of Thermoplastic Pressure Piping Irrigation Systems,xe2x80x9d states xe2x80x9cWhen installing piping systems that include joints that are self restraining (for example, elastomeric seal type) thrust blocking may be necessary at certain points in the system, such as changes in direction, in order to prevent possible disengagement of the fitting from the pipe.xe2x80x9d
The present invention is directed toward a thrust plug that performs the functions of both capping or plugging an end of a length of pipe and providing a surface against which a thrust block can be cast. In a broad sense, the thrust plug of the present invention comprises a plug affixed to a base for engagement with a thrust block and against which a thrust block can be directly cast. The thrust plug of the present invention preferably reversibly caps or plugs the length of pipe.
Additionally, the thrust plug can have optional structures such as one or more stabilizing structures that add positional stability to the thrust plug relative to a thrust block, such as one or more of the following: an outer flange extending from at least a portion of the periphery of the base 14 toward the thrust block, other flanges, an extension of the plug 12 extending toward the thrust block, gussets, standoffs, etc. The plug preferably has a portion that is like a length of pipe, i.e., cylindrical. In the alternative, or in addition, the plug can have a portion that is tapered (e.g., frustoconical or like an end of a hand-dipped candle or like the tip of a classically drawn tear drop), and most-preferably slightly tapered.